The best continuous flow water heater depends on fuel, installation location, and how many fixtures need hot water at once. The Rheem is best for high-demand homes with outdoor natural-gas installation; the FOGATTI suits indoor natural-gas setups; and the APUS is a higher-output electric option. The Westinghouse is better for smaller electric needs and smart-home controls, while the VELPAX is designed for portable outdoor use. Compare rated flow carefully: actual performance can change with incoming water temperature and demand.
| Product | Fuel | Best suited for | Listed flow |
|---|---|---|---|
| Rheem RTG Series | Natural gas | Outdoor whole-home use | 8.4 GPM at a 35°F rise |
| FOGATTI | Natural gas | Indoor residential use | 5.1 GPM |
| APUS 27kW | Electric | Higher-demand electric use | Up to 6.5 GPM |
| Westinghouse 14kW | Electric | Smaller electric demand | 3.4 GPM under stated conditions |
| VELPAX portable | Propane | Camping and outdoor showers | Up to 4.76 GPM |
Rheem RTG Series Outdoor Natural Gas
Best for: Larger households looking for a high-capacity outdoor natural-gas unit. Rheem lists an output of 8.4 GPM at a 35°F temperature rise and 180,000 BTU per hour, with support for several simultaneous hot-water uses. Its outdoor installation eliminates the need for indoor venting, and its non-condensing design has a listed 0.82 Uniform Energy Factor.
This model is a strong choice when household demand and an outdoor installation location are priorities. Its rated flow is tied to a specific temperature rise, so it should not be treated as a guaranteed flow rate in every climate or installation. Consideration: It is designed for outdoor installation, and the listing recommends installation by a qualified installer.
FOGATTI Indoor Natural Gas Tankless Heater
Best for: Buyers seeking an indoor natural-gas continuous flow heater. The listed specifications include 120,000 BTU per hour and a 5.1 GPM flow rate. FOGATTI describes water servo technology and temperature sensors that adjust water flow and gas input, with temperature variation stated as within ±1°F.
Choose this model if you want an indoor gas unit and its listed flow aligns with your household’s needs. The manufacturer says it can serve multiple outlet points, but actual simultaneous use depends on flow demand and incoming water temperature. Consideration: This is an indoor gas appliance; confirm that the proposed location and installation requirements suit the home before buying.
APUS 27kW Electric Tankless Heater
Best for: Buyers considering a high-output 240V electric model for several residential hot-water uses. APUS lists up to 6.5 GPM and describes its intended use as supporting three to four simultaneous uses. The digital display allows temperature adjustment from 86°F to 140°F in 1°F increments, and a memory function recalls the previous setting.
Its self-modulating heating system adjusts output according to water flow and temperature demand. Because it has no storage tank, it does not repeatedly reheat stored water while idle. Consideration: The listed maximum flow is not a constant guarantee; inlet temperature, selected outlet temperature, and household demand affect actual flow. Check electrical capacity and installation requirements for a 27kW appliance.
Westinghouse 14kW Electric With Wi-Fi
Best for: Households with more modest electric hot-water demand that value app and voice controls. The manufacturer lists a 3.4 GPM flow rate when inlet water is 62°F and the outlet is set to 105°F, describing that condition as suitable for two water points. It also lists Alexa and Google Home compatibility, temperature memory, and a compact wall-mounted design.
At 240V, the unit requires a dedicated 60A double-pole breaker and 6 AWG wire, according to the product details. Consideration: The required dedicated circuit is an important installation constraint, and its stated flow is tied to specific inlet and outlet temperatures. It is better suited to lower demand than the higher-output options listed here.
VELPAX Portable Propane Water Heater
Best for: Campers and other users who need on-demand hot water outdoors rather than a fixed whole-house system. VELPAX lists 82,000 BTU per hour and a maximum output of 4.76 GPM. The package includes a five-mode shower head with a pause button, plus overheat and 20-minute overtime protection.
Its portable design makes it a different kind of continuous flow option from the residential wall-mounted models. Check the stated gas and water pressure requirements before use. Consideration: This model is described for outdoor use, so it is not the choice for buyers seeking a permanently installed indoor whole-home heater.
Buying Guide: How To Choose A Continuous Flow Water Heater
How much hot-water flow does your household need?
Start by estimating which fixtures may run at the same time, such as a shower and kitchen faucet. Compare that combined demand with the heater’s flow rating, while checking the conditions behind the rating. A unit’s output can fall when incoming water is colder or when the requested temperature rise is greater. For example, Rheem provides a flow figure at a 35°F rise, and Westinghouse states its rate at specific inlet and outlet temperatures.
Should you choose gas or electric?
Gas models may suit households seeking higher whole-home flow, but they require an appropriate gas supply and installation setup. Electric models avoid gas use but need adequate electrical service. The Westinghouse specifies a dedicated 60A circuit and 6 AWG wire; the APUS is a 27kW, 240V model. Have an installer assess the home’s capacity before selecting an electric unit.
Does installation location matter?
Yes. The Rheem is intended for outdoor installation, while the FOGATTI is an indoor model and the VELPAX is designed for outdoor portability. Confirm the appliance’s intended location and installation needs before purchase. A portable camping heater is not a substitute for a fixed indoor whole-house system.
What controls and features are useful?
Digital temperature displays and memory settings can make it easier to restore a preferred setting. Wi-Fi and voice controls are listed on the Westinghouse model, while the APUS offers 1°F adjustment and setting memory. Treat these as convenience features; flow capacity, fuel availability, and installation requirements should come first.
Frequently Asked Questions
What is a continuous flow water heater?
It heats water as it passes through the unit instead of storing a tank of hot water. Hot-water availability and flow depend on the model’s capacity and operating conditions.
Can a tankless heater supply several fixtures at once?
Some models are designed for simultaneous use, but capacity varies. Compare the product’s flow rate with combined fixture demand and account for incoming water temperature.
Are electric tankless heaters suitable for whole-home use?
They can be, if their output meets household demand and the home’s electrical service supports the unit. Check the model’s voltage, power, and circuit requirements.
Does a higher GPM rating always mean better performance?
No. Flow figures may depend on temperature rise and other stated conditions. Review the rating conditions and compare them with your climate and desired hot-water temperature.
Can a portable propane model be installed indoors?
The VELPAX listed here is described for outdoor use. Choose a model specifically designed for the intended location and follow its installation instructions.